From mboxrd@z Thu Jan 1 00:00:00 1970 From: grygorii.strashko@ti.com (Grygorii Strashko) Date: Fri, 13 Nov 2015 20:09:06 +0200 Subject: [PATCH] clocksource: arm_global_timer: fix suspend resume In-Reply-To: <87y4e1ol0g.fsf@saruman.tx.rr.com> References: <1447431951-23713-1-git-send-email-grygorii.strashko@ti.com> <87a8qhq284.fsf@saruman.tx.rr.com> <56461688.1090809@ti.com> <87y4e1ol0g.fsf@saruman.tx.rr.com> Message-ID: <56462742.3020300@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 11/13/2015 07:40 PM, Felipe Balbi wrote: > > Hi, > > Grygorii Strashko writes: >> On 11/13/2015 06:43 PM, Felipe Balbi wrote: >>> >>> Hi, >>> >>> Grygorii Strashko writes: >>>> Now the System stall is observed on TI AM437x based board >>>> (am437x-gp-evm) during resuming from System suspend when ARM Global >>>> timer is selected as clocksource device - SysRq are working, but >>>> nothing else. The reason of stall is that ARM Global timer loses its >>>> contexts. >>>> >>>> The reason of stall is that ARM Global timer loses its contexts during >>>> System suspend: >>>> GT_CONTROL.TIMER_ENABLE = 0 (unbanked) >>>> GT_COUNTERx = 0 >>>> >>>> Hence, update ARM Global timer driver to reflect above behaviour >>>> - save GT_CONTROL.TIMER_ENABLE during suspend and restore on resume; >>>> - ensure clocksource and clockevent devices have coresponding flags >>>> (CLOCK_SOURCE_SUSPEND_NONSTOP and CLOCK_EVT_FEAT_C3STOP) set >>>> depending on presence of "always-on" DT property. >>>> >>>> CC: Arnd Bergmann >>>> Cc: John Stultz >>>> Cc: Felipe Balbi >>>> Cc: Tony Lindgren >>>> Signed-off-by: Grygorii Strashko >>>> --- >>>> drivers/clocksource/arm_global_timer.c | 23 +++++++++++++++++++++++ >>>> 1 file changed, 23 insertions(+) >>>> >>>> diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c >>>> index a2cb6fa..1bbaf64 100644 >>>> --- a/drivers/clocksource/arm_global_timer.c >>>> +++ b/drivers/clocksource/arm_global_timer.c >>>> @@ -51,6 +51,8 @@ static void __iomem *gt_base; >>>> static unsigned long gt_clk_rate; >>>> static int gt_ppi; >>>> static struct clock_event_device __percpu *gt_evt; >>>> +static bool gt_always_on; >>>> +static u32 gt_control; >>>> >>>> /* >>>> * To get the value from the Global Timer Counter register proceed as follows: >>>> @@ -168,6 +170,9 @@ static int gt_clockevents_init(struct clock_event_device *clk) >>>> { >>>> int cpu = smp_processor_id(); >>>> >>>> + if (!gt_always_on) >>>> + clk->features |= CLOCK_EVT_FEAT_C3STOP; >>>> + >>>> clk->name = "arm_global_timer"; >>>> clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | >>>> CLOCK_EVT_FEAT_PERCPU; >>>> @@ -195,12 +200,25 @@ static cycle_t gt_clocksource_read(struct clocksource *cs) >>>> return gt_counter_read(); >>>> } >>>> >>>> +static void gt_suspend(struct clocksource *cs) >>>> +{ >>>> + gt_control = readl(gt_base + GT_CONTROL); >>>> +} >>>> + >>>> +static void gt_resume(struct clocksource *cs) >>>> +{ >>>> + /* enables timer on all the cores */ >>>> + writel(gt_control & GT_CONTROL_TIMER_ENABLE, gt_base + GT_CONTROL); >>> >>> do you really need to save context if all you restore is TIMER_ENABLE >>> bit ? seems like you could skip gt_suspend altogether. Is there really a >>> situation where this driver is running and GT isn't enabled ? >> >> Now It's not. It's always enabled. I did it because .suspend() is called for >> all registered clock sources regardless of their usage. So, potentially >> in the future, at the moment when .suspend() is called it might be disabled >> (for example, .enable/disable() callbacks can be added and, if ARM Global timer >> will not be registered as sched_clock, it will be possible to keep it disabled >> if not used now). >> >> But It's not essentially now - I can update it and drop save restore. >> Pls, confirm. > > I think it's best to skip suspend completely. You're not restoring > anything you saved during suspend, unless you meant | where you used &. > I didn't get it - I'm restoring one bit(0) only. -- regards, -grygorii